Nuvia (United Kingdom)

With increasing global population, the gap between the supply and demand for water is widening and poses a threat to human existence. In the face of water scarcity, urban wastewater is increasing in its attention as an alternate water source for crop production. However, several challenges such as toxicity hazards, salinity build-up and health concerns have been identified with the use of wastewater in agriculture. There are several technological solutions that can help ameliorate or lower the level of contamination associated with using wastewater for irrigation. This paper explores the use of some irrigation technologies to abate the toxicity and health concerns associated with wastewater irrigation. The paper identifies some decision parameters for the selection of identified irrigation technologies and subjects them to multi-criteria decision analysis (MCDA) to rank them based on the level of exposure of the crop and irrigator/field worker to contamination among other relevant criteria. This paper validates that limiting the contact of the wastewater with the edible parts of the crop, especially for leafy vegetables, can minimize contamination to the crop and field workers. Though not totally without constraints, the identified irrigation methods present prospects for a cleaner and more sustainable production with regard to wastewater usage in agriculture. Sub-surface drip irrigation systems were identified as the best irrigation system for filtered and treated wastewater followed by surface drip and pitcher irrigation. Irrigators can fall back on some of these identified methods for wastewater application for sustainable crop production and maximized food safety.

The IDEAS Guidelines [Doerfel, H., et al General Guidelines for the Estimation of Committed Effective Dose from Incorporation Monitoring Data. Report FZKA 7243, Forschungszentrum Karlsruhe, GmbH (2006); Castellani, C. M., Marsh, J. W., Hurtgen, C., Blanchardon, E., Berard, P., Giusani, A. and Lopez, M. A. IDEAS Guidelines (Version 2) for the Estimation of Committed Doses from Incorporation Monitoring Data. EURADOS Report 2013-01, Braunschweig (2013)] provide a structured approach to the assessment of intakes of radionuclides. In order to check that the guidelines, when applied to typical monitoring programmes, lead to reliable assessments, a number of numerically-generated datasets have been constructed and assessed using the guidelines. The dose and intake obtained by the assessment can be compared with the 'true' dose and intake. In this way, the accuracy of the IDEAS assessment process can be examined when applied to monitoring programmes that are typically used in the nuclear industry. The simulations focus on assessments carried out as a result of elevated (239)Pu activities in routine urine samples, which lead to follow-up urine and faecal samples being provided. Cases where the assessor makes the correct initial assumption about lung solubility can be compared with cases where this initial choice is wrong. The results of these simulations and the implication for the use of monitoring programmes are discussed.

The paper relates to the determination of the amount of nuclear material contained in a closed, concrete lined vault at the Aktau fast breeder reactor in Kazakhstan. This material had been disposed into the vault after examination in an experimental hot cell directly above the vault. In order to comply with IAEA Safeguards requirements it was necessary to determine the total quantities of nuclear materials — enriched uranium and plutonium — that were held with Kazakhstan. Although it was possible to determine the inventory of all of the accessible nuclear material — the quantity remaining in the vault was unknown. As part of the Global Threat Reduction Programme the UK Government funded a project to determine the inventory of these nuclear materials in this vault. This involved drilling three penetrations through the concrete lined roof of the vault; this enabled the placement of lights and a camera into the vault through two penetrations; while the third penetration enabled a lightweight manipulator arm to be introduced into the vault. This was used to provide a detailed 3D mapping of the dose rate within the vault and it also enabled the collection of samples for radionuclide analysis. The deconvolution of the 3D dose rate profile within the vault enabled the determination of the gamma emitting source distribution on the floor and walls of the vault. The samples were analysed to determine the fingerprint of those radionuclides producing the gamma dose — namely 137Cs and 60Co — to the nuclear materials. The combination of the dose rate source terms on the surfaces of the vault and the fingerprint then enabled the quantities of nuclear materials to be determined. The project was a major success and enabled the Kazakhstan Government to comply with IAEA Safeguards requirements. It also enabled the UK DECC Ministry to develop a technology of national (and international) use. Finally the technology was well received by IAEA Safeguards as an acceptable methodology for future studies.

A real-time internal dose assessment exercise has been conducted in which participants were required to make decisions about sampling requirements, seek relevant information about the 'incident' and make various interim dose assessments. At the end of the exercise, each participant was requested to make a formal assessment, providing statements of the methods, models and assumptions used in that assessment. In this paper we describe how the hypothetical assessment case was set up and the exercise was conducted, the responses of the participants and the assessments of dose that they made. Finally we discuss the lessons learnt from the exercise and suggest how the exercise may be adapted to a wider range of participants.

In a recent epidemiological study, Bayesian uncertainties on lung doses have been calculated to determine lung cancer risk from occupational exposures to plutonium. These calculations used a revised version of the Human Respiratory Tract Model (HRTM) published by the ICRP. In addition to the Bayesian analyses, which give probability distributions of doses, point estimates of doses (single estimates without uncertainty) were also provided for that study using the existing HRTM as it is described in ICRP Publication 66; these are to be used in a preliminary analysis of risk. To infer the differences between the point estimates and Bayesian uncertainty analyses, this paper applies the methodology to former workers of the United Kingdom Atomic Energy Authority (UKAEA), who constituted a subset of the study cohort. The resulting probability distributions of lung doses are compared with the point estimates obtained for each worker. It is shown that mean posterior lung doses are around two- to fourfold higher than point estimates and that uncertainties on doses vary over a wide range, greater than two orders of magnitude for some lung tissues. In addition, we demonstrate that uncertainties on the parameter values, rather than the model structure, are largely responsible for these effects. Of these it appears to be the parameters describing absorption from the lungs to blood that have the greatest impact on estimates of lung doses from urine bioassay. Therefore, accurate determination of the chemical form of inhaled plutonium and the absorption parameter values for these materials is important for obtaining reliable estimates of lung doses and hence risk from occupational exposures to plutonium.

The Springfields facility manufactures nuclear fuel products for the UK’s nuclear power stations and for international customers. Fuel manufacture is scheduled to continue into the future. In addition to fuel manufacture, Springfields is also undertaking decommissioning activities. Today it is run and operated by Springfields Fuels Limited, under the management of Westinghouse Electric UK Limited. The site has been operating since 1946 manufacturing nuclear fuel. As part of the decommissioning activities, there was a need was to quantify contamination in a large redundant building. This building had been used to process uranium derived from uranium ore concentrate but had also processed a limited quantity of recycled uranium. The major non-uranic contaminant was Tc-99. The aim was to be able to identify any areas where the bulk activity exceeded 0.4 Bq/g Tc-99 as this would preclude the demolition rubble being sent to the local disposal facility. The problems associated with this project were the presence of significant uranium contamination, the realisation that both the Tc-99 and the uranium had diffused into the brickwork to a significant depth and the relatively low beta energy of Tc-99. The uranium was accompanied by Pa-234m, an energetic beta emitter. The concentration/depth profile was determined for several areas on the plant for Tc-99 and for uranium. The radiochemical analysis was performed locally but the performance of the local laboratory was checked during the initial investigation by splitting samples three ways and having confirmation analyses performed by 2 other laboratories. The results showed surprisingly consistent concentration gradients for Tc-99 and for uranium across the samples. Using that information, the instrument response was calculated for Tc-99 using the observed diffusion gradient and averaged through the full 225 mm of brick wall, as agreed by the regulator. The Tc-99 and uranium contributions to the detector signal were separated using a simple absorber, which essentially eliminated the Tc-99 count rate and reduced the uranium contribution only marginally. The outcome of the project was that it was possible to demonstrate that the complete building met the criterion for acceptance at the local waste facility.

Kazakhstan’s BN-350 fast reactor was shut down in 1999 and is in the process of being decommissioned in preparation for Safestore. A key achievement during 2010 was the removal of the known inventory of spent nuclear fuel (SNF) from the reactor to off-site secure storage. As a complementary activity, surveys of areas of the fuel discharge route where it was considered possible for fuel pins or fuel residues to have collected over many years of operation were also arranged to confirm that no significant amounts of fuel of remained at the plant. This paper reports on the remote radiation and visual (video and still photograph) surveys undertaken on the following areas of the BN-350 spent fuel route: • The waste storage repository or vault underneath the Post-Irradiation Examination Hot Cell in which non-destructive and destructive examination of irradiated fuels was undertaken throughout the operating life of the reactor. • The fuel transfer and washing cells within which irradiated fuel sub-assemblies were processed and residual sodium coolant removed. • The fuel storage ponds. Man access to several areas (particularly the waste vault) was not possible due to very high radiation levels from stored βγ-active wastes or residual contamination and in these cases specially engineered remote camera and radiation detector deployment systems were developed and used. In other areas, such as the ponds, limited man access was possible under prepared and controlled conditions. The survey results, together with associated radiochemical and radiation dose rate analysis, demonstrated that, despite several recorded handling incidents during Hot Cell operations, the maximum estimated amounts of nuclear material which could remain at BN-350 were sufficiently low to give no major safeguards concerns. The data also provides key information to guide decommissioning and dismantling planning in the future.

Part of the nuclear site restoration and delicensing process involves the characterisation and assessment of below-ground drainage systems. Site restoration is currently underway at Harwell in Oxfordshire where there is a complex drainage system that has developed over more than 70 years. Drainage decommissioning involves visual inspections, jet-washing and radiological surveys prior to final grouting. Prior to decommissioning, the structural and radiological condition of the network was unknown and now requires characterisation and assessment against defined clean-up criteria before the land can be released for future use. This paper outlines the application of an innovative Geographic Information System (GIS) and data management methodology to assess the structural and radiological condition of the drainage network at Harwell. The approach demonstrates the importance of efficient data collection and storage, implemented using UKAEA’s IMAGES land quality data management system. It also details several GIS techniques that can be utilised to accurately position below-ground surveys and record pipe material and diameter for surveyed drain sections. The aim of the monitoring process is to identify any activity which exceeds the delicensing criteria set by the Nuclear Installations Inspectorate (NII). The relevant criteria are the residual activity and the risk to a future site occupier. The maximum missable activity for each pipe class was determined by considering instrumentation characteristics and natural background radiation levels. The equipment used (a caesium iodide scintillation probe connected to a ratemeter), was limited by the small diameter of some drains. The hypothesis chosen was that residual activity was most likely to lie along the base of the pipe, given that the drains generally ran with only a limited depth. The response was measured for 137Cs gamma radiation and then used to calculate the net count rate for a variety of pipe configurations. Variability of the data was investigated in relation to static probe response and variations in counts per second along a pipe length. Analysis of the data using GIS showed clear spatial patterns, indicating systematic variability within each pipe material and diameter class. Clearance criteria were derived from this analysis and will be used to establish whether the specific sections of drain can remain in situ or require removal. This approach improves safety and cost performance of the decommissioning process and ensures that a transparent and auditable record of the status of the drainage system remains for the future re-use of the land as the Harwell Science and Innovation Campus.